In vehicles such as automobiles, a gas processing device for exhaust gas purification is loaded in order to remove harmful components such as carbon monoxide, hydrocarbons, nitrogen oxides, etc. contained in an exhaust gas of the engine. Such a gas processing device is generally composed of a processing structure formed in a cylindrical shape such as a catalytic carrier, a metal casing for accommodating the processing structure and a holding material attached to the processing structure and disposed in a gap between the processing structure and the casing.
The holding material disposed in a gap between the processing structure and the casing is required to have, in combination, a function of safely holding the processing structure so that the processing structure is prevented from colliding the casing and breaking by vibrations or the like while the automobile is running, as well as a function of sealing so that unpurified exhaust gas does not leak out from the gap between the processing structure and the casing. In order to hold the processing structure safely, it is required to hold the processing structure at a prescribed surface pressure. There is a problem that a surface pressure is lowered by repeated compression accompanied by heating.
For example, Patent Document 1 discloses a holding material having a high surface pressure obtained by combining silica fibers and alumina sol.